Rotational and Linear Dynamics Compared
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Slide 7-36
Interpreting Torque
Torque is due to the component of the force perpendicular to the
radial line.
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 rF rFsin
Slide 7-25
Signs and Strengths of the Torque
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Slide 7-27
Example Problem
Revolutionaries attempt to pull down a statue of the Great Leader
by pulling on a rope tied to the top of his head. The statue is 17 m
tall, and they pull with a force of 4200 N at an angle of 65° to the
horizontal. What is the torque they exert on the statue? If they are
standing to the right of the statue, is the torque positive or
negative?
© 2010 Pearson Education, Inc.
Slide 7-28
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
Newton’s Second Law for Rotation
  /I
I = moment of inertia. Objects with larger moments of inertia are
harder to get rotating.
I   mi ri
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2
Slide 7-34
Moments of Inertia of Common Shapes
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Slide 7-35
Example Problem
How long does it take the small mass to fall 1.0 m when
released from rest?
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Slide 7-40
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.